The present invention relates to an adjustable throttle valve consisting of a single or multi-part housing and having a control part and a throttle part, the throttle part containing a two-way seating valve with an axially movable hydraulically operated throttle piston which on one side connects a reserve supply channel via an annular restrictor with a consumption channel. The annular restrictor is formed between a seating surface of the throttle piston and a corresponding seating of the housing and is open to a greater or a smaller extent according to the axial position of the throttle piston, while on the other side it has a hydraulically actuated control surface connected to the reserve supply channel via a feed channel having a restrictor and to the consumption channel via a discharge channel. The said discharge channel has an aperture which is adjustable via the control part and which serves to regulate the pressure applied to the control surface, the said pressure determining the movement and position of the throttle piston.
Throttle valves of this kind are generally known and are used in many types of units. Among their numerous applications there are many, such as hydraulic presses and heavy-duty cranes, in which despite the size of the plant and the high hydraulic operating pressure, very precise movements have to be performed, so that exacting demands are made on the operating precision and accuracy of the throttle valves.
Unfortunately, the known throttle valves of the foregoing type only partly or inadequately satisfy the precision desirable for optimum accuracy of operation.
In the first place, conventional throttle valves involve excessive adjusting forces in the control part, which is a disadvantage from an economic point of view. In the second place, these known throttle valves involve excessive switching time for a number of applications, which detracts from their suitability for use. In addition, these known throttle valves are exposed to excessive wear, which unduly shortens their service life.